Most smokers begin during early adolescence, and most adolescent smokers want to quit and have tried unsuccessfully. The evidence for cessation counseling for adolescents is limited; teenagers rarely think of quitting with assistance. This proposal examines the effectiveness of adolescent smoking cessation interventions in pediatric primary care settings in the American Academy of Pediatrics (AAP) Pediatric Research in Office Settings (PROS) practice-based research network (PBRN) of 1768 clinicians in 725 primary care pediatric practices. We will use self-study and distance learning clinician training modules for smoking cessation, practice recruitment and randomization protocols and adolescent measures developed and tested in pilot work supported by AHRQ (1R03 HS014418-01) and NCI (5R21CA122705-02). Building on these preliminary studies, we propose a group randomized trial of guideline-based smoking cessation counseling interventions with adolescents in pediatric primary care practice. Our specific aims are to demonstrate providers' fidelity to guidelines for tobacco counseling and delivery of cessation interventions, including systematic screening using charting tools and linkages to adjunct materials, including web resources. We will also assess the impact of primary care provider counseling interventions on adolescent smoking cessation. We hypothesize that adolescents who receive guideline-based clinician delivered smoking cessation counseling at primary care visits will be more likely to make quit attempts, and be more likely to remain successfully abstinent at 6 months and 1 year after the intervention. We will randomize providers from 126 PROS practice sites, 18,900 adolescents presenting for care will complete short baseline surveys prior to their clinical visits, and 1890 smokers will be surveyed by phone 2-4 weeks after their visits to assess quit attempts and short-term cessation, and again at 6 and 12 months to evaluate intermediate and long-term adolescent smoking cessation outcomes and self-reported quitters will provide saliva samples for cotinine validation. We will describe patterns of smoking among youth, and explore whether receiving interventions affects motivation, quitting, abstinence/relapse adjunct use, and other smoking behaviors. Our long-term goal is to improve clinical preventive services for adolescent tobacco cessation. Evidence from primary care community-based pediatricians has great potential for rapid dissemination and translation of effective interventions into practice.